#P661F. Primes in Interval

Primes in Interval

Description

You are given two integers a and b (a ≤ b). How many prime numbers are there on the interval from a to b, inclusive?

The input contains two integers a and b (2 ≤ a ≤ b ≤ 1 000 000), separated by a single space.

Output a single integer — the number of primes between a and b, inclusive.

Input

The input contains two integers a and b (2 ≤ a ≤ b ≤ 1 000 000), separated by a single space.

Output

Output a single integer — the number of primes between a and b, inclusive.

10 20<br>
23 23<br>
271 566<br>
4<br>
1<br>
46<br>